Genetic, clinical and molecular characterization of inherited colon cancer risk is the focus of our present and long-term work. Genes for the rare syndromes of this malignancy have been found but account for only a small fraction of the estimated one-third of colon cancer cases that arise from inheritance. The aims of our present proposal are 1) to identify the susceptibility genes that give rise to the more common inherited risk, 2) to continue to define the associated phenotype, 3) to establish molecular characteristics of the high-risk families and known syndromes with gene expression profiling and 4) to examine the expression of specific APC/beta-catenin pathway genes as potential diagnostic markers. Together these goals will provide tools to identify persons with inherited risk. We will accomplish the aims as follows: We will identify colon cancer susceptibility loci by linkage analysis of large high-risk colon cancer families in which the known syndromes of colon cancer have been ruled out. Colonoscopy is performed on family members to define polyp expression, both for phenotype and linkage analysis. Gene expression profiling by microarray analysis is performed on normal appearing and neoplastic colonic tissue obtained at colonoscopy and immediately preserved. Profiling will assist both in identification of susceptibility pathways and in establishing characteristic expression profiles in the inherited colon cancer settings. Gene expression patterns will be examined in the normal and neoplastic tissue of the high-risk families and compared to similar samples from families with familial adenomatous polyposis (FAP), attenuated FAP, hereditary nonpolyposis colorectal cancer, sporadic adenomatous polyp cases and normal controls. Gene expression will be examined using a reference RNA and analyzed by supervised (and later unsupervised) analysis of the groups. Finally the expression of four specific APC/beta-catenin pathway marker genes will be examined in neoplastic and normal tissues from the above groups by both real-time quantitative PCR and by in situ RNA hybridization. Previous microarray experiments in our laboratory indicate that expression of these genes is frequently perturbed in sporadic polyps, making them attractive markers of cancer susceptibility to evaluate APC/beta-catenin pathway contributions in undefined forms of inherited colon cancer, as compared to defined inherited syndromes. [unreadable] [unreadable]